In one aspect, this invention pertains to a method of minimizing phosphonium ion ligand degradation products that are formed in a reaction of a polyolefin in the presence of a transition metal-triorganophosphine ligand complex catalyst to yield as a product, by-product, or intermediate product a conjugated functionalized olefin. As used herein, the term “polyolefin,” or its equivalent “polyunsaturated olefin,” refers to an olefin having a plurality of unsaturated carbon-carbon double bonds. The term “conjugated functionalized olefin” shall refer herein to a compound comprising a carbon-carbon double bond conjugated to an α-electron-withdrawing group, such as an aldehyde, ketone, ester, acid, or nitrile. As an example, this invention pertains to a method of minimizing the formation of phosphonium ion ligand degradation products that are formed in the hydroformylation of a polyolefin with carbon monoxide in the presence of hydrogen and a transition metal-triorganophosphine ligand complex catalyst to produce an α,β-unsaturated aldehyde.
In a second aspect, this invention pertains to a process of minimizing phosphonium ion ligand degradation products that are formed in a reaction of an unconjugated functionalized olefin, such as an unconjugated unsaturated ester, in the presence of a transition metal-triorganophosphine ligand complex catalyst, to form as a product, by-product, or intermediate product a conjugated functionalized olefin, such as an α,β-unsaturated ester. Isomerization reactions exemplify this type of reaction.
In a third aspect, this invention pertains to a process for the reversion of phosphonium ion ligand degradation products back to useful triorganophosphine ligands.
Processes catalyzed by transition metal-triorganophosphine ligand complex catalysts are described in the prior art, for example, in the following U.S. Pat. Nos.: 6,369,283, 6,191,324, 5,886,237, 5,693,851, and 5,495,041. Such useful processes include hydroformylation, hydroacylation, hydroesterification, carbonylation, and hydrocyanation. The products of these reactions include, for example, aldehydes, ketones, esters, acids, and nitriles, respectively, which find widespread utility in the chemical industry.
The prior art, as illustrated by U.S. Pat. No. 6,191,324, discloses a carbonylation process wherein a polyunsaturated olefin, such as butadiene, is hydroformylated with carbon monoxide in the presence of hydrogen and a hydroformylation catalyst comprising a Group VIII transition metal-triorganophosphine ligand complex catalyst, to form an unsaturated aldehyde. The polyunsaturated olefin conversion may range from about 27 up to 99 percent. Disadvantageously, the use of polyunsaturated olefin presents a problem not encountered when a monounsaturated olefin is used, namely, that the rate of triorganophosphine ligand usage can exceed an acceptable level. As a consequence, ligand degradation products form in unacceptable yield. The loss of useful ligand may disadvantageously reduce catalyst activity. Moreover, make-up ligand must be added to the process to maintain catalytic activity and to prevent catalytic metal from depositing out of the reaction fluid. The economic disadvantages resulting from ligand loss, reduced catalyst activity, and the need for make-up ligand diminish the prospects for commercializing polyunsaturated olefins as reactants in such processes. As a further disadvantage, the ligand degradation products themselves may be sufficiently basic to catalyze the formation of undesirable heavies with accompanying losses in selectivity and yield to desired products. Heavies by-products also necessitate additional separation and purification efforts, if desired products of acceptable purity are to be obtained.
Certain academic and patent publications disclose the reactions of activated olefins with triorganophosphines to form zwitter-ionic phosphonium salts. See for example, A. Bényei et al., Journal of Molecular Catalysis, 84 (1993), 157-163; and M. A. Shaw and R. S. Ward, “Addition Reactions of Tertiary Phosphorus Compounds with Electrophilic Olefins and Acetylenes,” Topics in Phosphorus Chemistry, 7 (1972), 1-35, as well as US-A1-2002/0183196 and EP-A1-1,249,455. Such publications may suggest that the ligand degradation products formed during reactions of polyunsaturated olefins in the presence of triorganophosphine ligands might also comprise zwitter-ionic phosphonium salts.
Reference is also made to co-pending International Patent Application Serial No. PCT/US04/012246, entitled “Aldehyde and Alcohol Compositions Derived from Seed Oils,” filed on April 22, 2004, in the names of Zenon Lysenko et al., which discloses the hydroformylation of polyunsaturated olefins derived from seed oils in the presence of transition metal-organophosphorus ligand complex catalysts for the purpose of preparing specific compositions of mono-, di-, and tri-formylated fatty acid esters. This international patent application does not recognize the problem of organophosphine ligand loss to phosphonium ion degradation products or any solution to such a problem.
In view of the above, it would be desirable to discover a process that minimizes formation of ligand degradation product(s) during reaction of a polyolefin in the presence of a transition metal-triorganophosphine ligand complex catalyst to form as an product, by-product, or intermediate product a compound having a carbon-carbon double bond conjugated to an α-electron-withdrawing group, such as aldehyde, ketone, ester, acid, or nitrile. It would be more desirable if such a minimization process could be implemented easily and at reasonable cost. Discovery of such a minimization process would reduce the loss of catalytic metal and the need for make-up ligand; would provide for more consistent catalyst activity; and would reduce the production of heavies and the problems associated therewith. Additionally, it would be desirable to discover a process that reverts phosphonium ion ligand degradation products, once formed and present in reaction product fluids, back to useful triorganophosphine ligands. Such a reversion process would beneficially remove phosphonium ion ligand degradation products from reaction product fluids, conserve useful ligands, and reduce the detrimental effects such ligand degradation products produce.